Boxes and similar three-dimensional packages are often manufactured by first cutting a flat sheet of plastic, cardboard or paper into a shape which can be folded into a box. These flat shapes are commonly referred to as "blanks." It has long been known that the use of performed creases known as "score lines" allows blanks to be easily folded. By creasing the blank, the manufacturer or packager can fold the blank precisely where it should be folded. For example, U.S. Pat. No. 5,599,267 discloses, among other things, lining up score lines in plastic sheets with score lines in cardboard blanks to create cardboard boxes having windows which extend around two sides of a box.
While score lines may have been in use for quite some time, a number of disadvantages still surround prior attempts to inexpensively and easily create score lines, particularly in blanks made out of certain plastics. For example, many systems heat the plastic blank during scoring by means of heated platens and rules or using RF fields. Although a high-quality score results from such a process, the heating step results in added expense, increased safety considerations and slower production rates.
U.S. Pat. No. 5,302,435 discloses a plastic sheet with a ruled line for bending. The ruled line is a groove which has shallow and deep recess portions running along the length of the groove. In other words, the groove has alternating and generally-rectangular "hills" and "valleys" extending in the direction of the groove. The shallow portions are "chamfered" at the edges so that the generally rectangular hills have rounded edges which give the groove "a good touch feel." The chamfer is apparently necessary because, at the size ranges taught by the patent (0.3-1.5 mm), the edges of the shallow portions will not "have a good touch feel" when the package is bent at the scoring line. JP 64-40317, an earlier reference by the same applicant as the patent, also discloses a plastic sheet with a ruled line for bending and similarly-sized deep portion lengths (0.1-2.0 mm) and shallow portion lengths (0.3-3.0 mm). Both references suffer from the further disadvantage that the score line is visually distracting because the score line actually appears to be a perforation.
Accordingly, none of the foregoing references teaches an efficient manner of placing relatively smooth score lines in plastic blanks without the need to heat or specifically chamfer the high and low portions in the groove. There is, therefore, a need for blanks and a process for making same which overcomes these disadvantages.
The present invention meets these needs.